Well in the meantime, RAM is relatively inexpensive and not a difficult upgrade task another 256MB stick would make a difference, swapping out your existing 256MB stick for 2x512MB sticks would make a large difference. Whilst this might seem an expense you could avoid, I'm afraid that you are likely to continue to experience these types of problem and a very slow system.
For win XP 256MB is considered a minimum requirement and you are sharing some of your with an on-board video chip. When you start to run other programs you have to consider their minimum requirements also and add that to the overall minimum or you need for multi-applications.
